I tried a lot of audio editing/conversion software last days, but I still didn't find the software which can read the 48 kHz, 20 bits LPCM files.
The most of the software which can read LPCM files, gives just a 16 or 24 bits option, not 20 bits.

The workaround for me on this moment is the following:
I use DVD Decrypter and rip not just the audio, but the LPCM audio with the video as a VOB file. I found the program MPEG Mediator, http://www.mpeg-mediator.com, which can extract the audio from a VOB file as a WAV file.
The weird thing is that MPEG Mediator recognizes the VOB file as a file with 16 bits audio and also the extracted WAV file is a 48 kHz, 16 bits WAV file.